Training for a race means making sacrifices like going to bed early and putting aside hours on the weekends for long runs. But what about your precious after-work glass of wine? Would you be willing to give it up?

We took an informal poll of the TIME staffers who are currently training to run half-marathons in the fall. None of them cut out drinking completely, but they did cut down, and they all said they curbed their consumption before longer runs. “When I’m training for a race, I generally do not drink as a rule. On occasion — if I’m not running the following day — I might have a glass of wine or beer with dinner, but I try to avoid it as much as possible,” says Liz Ronk, LIFE.com’s photo editor, who is training to run Grete’s Great Gallop, a half-marathon taking place in New York City’s Central Park on Oct. 14. “From past experience, I’ve found that drinking alcohol equals a sluggish workout the following day.” (Stay tuned for ongoing updates and tips from our race-training TIME colleagues throughout the summer.)

Opinions among other running devotees vary: some say there’s no room for alcohol in their training plan, but others feel that their post-run brews are a well-deserved treat.

Interestingly, a 2009 study found that drinking and exercise appear to go hand in hand. The study of more than 230,000 men and women showed that alcohol drinkers were 10% more likely to participate in vigorous exercise than abstainers, and that heavy drinkers worked out 10 minutes more than moderate drinkers each week and 20 minutes more than non-drinkers.

So, what’s the healthiest thing to do? Everyone enjoys happy hour now and again, but does regular drinking do anything to derail your training? As usual, moderation is the key. “If your drinking regime includes a glass or two of wine at dinner or the occasional beer on a Friday evening, that’s not going to be a problem,” says Hal Higdon, author of Marathon: The Ultimate Training Guide. “It’s a problem when you go out on a Friday evening and hang out a bar for three hours and throw down a half a dozen bottles of beer.”

According to Higdon, there are a couple of reasons alcohol hurts your body during training:

Booze makes your body thirsty
“Drinking dehydrates you, and you’re in danger particularly when it’s a hot day,” says Higdon. Excessive drinking can also reduce your muscle blood flow which weakens them. Running when your legs are feeling a hangover could lead to injuries. “You cannot perform well when you’re drunk, and you might still be the next morning,” he says.

Many races offer runners a celebratory beer after the run, but although completing a distance event is well worth celebrating, Higdon says alcohol isn’t the ideal prize for athletes. “It compounds the dehydration,” he says. “[Races] offer the drinks because the runners like it and [the race] can get sponsorship money. It’s not as bad as having a cigarette company sponsor a race, but it might be the next worst thing.”

If you’re craving the taste of a refreshing beer post-race — or while you’re training — Higdon advises runners to consider a non-alcoholic brew. A 2011 study from the Technical University of Munich found that among men training for the Munich Marathon, those who drank non-alcoholic beer reported fewer illnesses and less inflammation than men who drank a placebo, suggesting that downing the occasional nonalcoholic beer could ease marathon recovery. Why? That’s not clear, but the authors speculated that the beverage might offer some healing powers because of its antioxidant compounds called polyphenols, which naturally prevent cell damage and boost immunity.

Drinking throws off your sleeping schedule
You need to be in tip-top shape when you’re training, and sleep deprivation can alter levels of important hormones as well as the body’s production of antibodies, which fend off illness. “Sleep loss is another [negative] factor that comes from drinking,” says Higdon. “When you’re training for a marathon, you likely need extra sleep. If you have an early training run after a night out, you’re not going to be able to train well.”

By not getting adequate sleep, you run the risk of getting sick, which could not only interfere with training, but could even sideline you on the big day. Not to mention that disrupted sleep throws your body’s circadian rhythm out of whack, and over time, that can put you at higher risk of diabetes, weight gain, heart attack and even breast cancer.

Bottom line: you don’t have to cut out all alcohol when you’re training, but it’s a good idea to limit your consumption and abstain before running days.

“There are basic lifestyle changes that you benefit from during training,” says Higdon. “Less drinking is one of them, less smoking is another, as is losing weight. Research suggests that a marathon lifestyle can add 6 to 9 years to your life.”